In 2018, a major oil and gas company commissioned InterMoor to perform
a study to explore the use of their proprietary Suction Embedded PLate Anchors (SEPLAs) technology for permanent use in one of their FPSO mooring systems.

The turret-moored FPSO vessel is located offshore West Africa in
approximately 475 meters of water. At the time, the FPSO was moored on a 9-leg temporary system which replaced the original 9-leg system installed during commissioning of the facility.

Scope of Work

Following the conclusions of the study, InterMoor was commissioned by the client to provide new SEPLAs for the FPSO and, through Maersk Supply Service, to install the new permanent mooring system. The offshore operations consisted in three phases:

• Phase 1: Installation of 9 SEPLA anchors and ground chains
• Phase 2: Disconnection and laydown of 9 temporary mooring lines and installation and hookup of the new permanent mooring lines
• Phase 3: Recovery of temporary anchors from the seabed and transport to shorebase

Installation of the new permanent system took place in the fourth quarter of 2019. InterMoor provided:

• Engineering and project management including offshore procedures and logistics
• Transportation of mooring chains and connectors to West Africa
• Fabrication and procurement of installation equipment
• Offshore personnel

 

Check out the video of our offshore operations:

 

Largest SEPLA Anchors

For the project, InterMoor designed and fabricated nine SEPLA anchors. At 28t each, they are amongst the largest SEPLA anchors ever fabricated and installed. To optimize their strength and to allow for the use of large 157mm mooring chain, InterMoor engineers customized the design of the anchors for the project.

InterMoor’s SEPLA system uses a suction follower (similar to a suction anchor) to embed a plate anchor deeply in the soil. The suction follower is retracted once the plate anchor is brought to design soil depth and can be used again and again to install additional plate anchors. The use of plate anchors installed through a retrievable suction pile is designed to provide significant savings to project costs while maintaining efficient anchoring of the offshore asset. To further lower operational expenditure, regular anchor handling vessels, namely the Maersk Maker and Maersk Achiever, were used to install the large SEPLAs and chain.

Find out more about SEPLA anchors


Acteon Companies Involvement

The FPSO is moored to the 9 SEPLA anchors with mooring lines consisting of chain-wire-chain. For a seamless delivery, InterMoor asked sister company Aquatic to provide reel drive system to spool the Sheathed Spiral Strand Wire onto the winch drums of the installation vessel, which in turn were used to lower the wire into the water.

The project was completed safely and on time.